Fuel injection system for an internal combustion engine

Abstract

A fuel injection system for an internal combustion engine includes an air suction pipe, a throttle valve located in the pipe, and a member, upstream of the throttle valve, which is actuatable by air flowing through the suction pipe so as to move a piston valve to dose a quantity of fuel to a fuel injection nozzle. The system includes a duct which bypasses the throttle valve, the duct having a valve which closes the duct when the throttle valve is closed and when the engine is above the idling speed. Dosing of fuel is thereby stopped during coasting of a vehicle, leading to decreased fuel consumption.

We claim: 
     
       1. A fuel injection system for an internal combustion engine with continuous fuel injection into a suction pipe for use with a vehicle having a clutch and gear box having at least one gear, said system comprising: a suction pipe;   a throttle valve located in the suction pipe;   a member upstream of the throttle valve, said member being actuatable by air flowing through the suction pipe so as to dose fuel to the engine;   a duct which bypasses the throttle valve;   a duct valve located in said duct capable of closing off said duct;   a control means for controlling the operation of the duct valve, with said means including: a first switch and means for actuating said first switch when the clutch is engaged; a second switch and means for actuating said second switch when a gear of the gear box is engaged; a third switch and means for actuating said third switch when the throttle valve is closed; a fourth switch and means for actuating said fourth switch when the engine speed is above the idle speed; and means for actuating the duct valve to close off the duct when the throttle valve is closed, the engine speed is above the idling speed, the clutch is engaged and a gear of the gear box is engaged.   
     
     
       2. A fuel injection system in accordance with claim 1 wherein said duct valve is a solenoid valve. 
     
     
       3. A fuel injection system in accordance with claim 2 wherein said duct valve is a diaphragm valve. 
     
     
       4. A fuel injection system in accordance with claims 1, 2 or 3 wherein said means for actuating the duct valve includes a solenoid valve, said switches being in a circuit in which the circuit of the solenoid valve, or a relay which controls the current of the solenoid valve, is located. 
     
     
       5. A fuel injection system according to claim 4, wherein the duct valve is optionally connected to a point of the suction pipe downstream of the throttle valve or to the atmosphere. 
     
     
       6. An internal combustion engine having a fuel injection system according to claim 1. 
     
     
       7. A vehicle having an engine according to claim 6.